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Biomedical subjects

F E Young

Publications and source records attributed to F E Young.

36 records · Page 2Linked to original sources
PubMed1977

Temperate Bacillus subtilis bacteriophage phi 3T: chromosomal attachment site and comparison with temperate bacteriophages phi 105 and SPO2.

The temperate Bacillus subtilis bacteriophage phi 3T contains within its genome a locus, designated thyP3, that encodes for a protein with thymidylate synthetase activity. Bacteriophage phi 3T is different from the two previously characterized temperate phages, phi 105 and SPO2, in: heteroimmunity, response to bacteriophage antisera, endonuclease digestion pattern, induction in the presence of 6-(p-hydroxyphenylazo)-uracil, and effect on the lytic cycle of bacteriophage phi 1. The mean burst size of phi 3T is 56. The dose response curve with bacteriophage phi 3T DNA is linear for transfection and transformation to the Thy+ phenotype. The inserted prophage has been mapped by PBS1 transduction; it is between chromosomal markers ilvA8 and gltA in the terminus of the chromosome. Thus thyP3 maps at a site separate from, but between, the bacterial markers thyA and thyB when thyP3 is in the prophage state.

Bacillus subtilis↗
PubMed1976

Analysis of autolysins in temperature-sensitive morphological mutants of Bacillus subtilis.

The content and distribution of autolysin were measured in temperature-sensitive morphological mutants of Bacillus subtilis. Strains RUB1000 and RUB1012 grew as rods at 30 C. At 45 C the mutants contained disproportionately less teichoic acid than peptidoglycan and grew as irregular spheres. The amount of enzyme that could be extracted from rods was at least 31 times the amount extracted from spheres. The rate of autolysis of cell walls was 7- to 28-fold greater in rods than in spheres. The low activity found associated with the cell walls of spheres was not compensated for by larger amounts of autolytic activity in the cytoplasm. No activity was found in the growth medium at either temperature. The failure of the mutant cells to autolyze was due to low amidase activity and relatively resistant cell walls. Revertants of RUB1012 were isolated that had 13, 23, and 55% of the normal proportions of teichoic acid when grown at the nonpermissive temperature. Cell walls from the revertants were as sensitive to added amidase as the wild-type strain. None of the revertant strains regained the wild-type ability to produce more amidase at 45 C. However, the deficiency in autolysin observed with RUB1012 was partially restored in revertants containing higher proportions of teichoic acid.

Amidohydrolases↗
PubMed1976

Bacteriophage resistance in Bacillus subtilis 168, W23, and interstrain transformants.

Strains of Bacillus subtilis 168 deficient in glucosylated teichoic acid vary in their resistance to bacteriophage infection. Although glucosylated teichoic acid is important for bacteriophage attachment, the results demonstrate that alternate receptor sites exist. Non-glucosylated cell wall mutants could be assigned to specific classes (gtaA, gtaB, gtaC) by their pattern of resistance to three closely related bacteriophages (phi25, phie, SP82). In addition to glucosylation, the type of teichoic acid was also important for bacteriophage attachment. B. subtilis strains 168 and W23 have different teichoic acids in their cell walls and have varied susceptibilities to bacteriophage infection. Transfer of bacteriophage resistance from strain W23 into a derivative of strain 168 was accomplished. The resistant bacteria obtained were imparied in their ability to adsorb bacteriophage and in their capacity to be transfected by bacteriophage deoxyribonucleic acid.

Adsorption↗
PubMed1976

Isolation and characterization of a mutant of Staphylococcus aureus deficient in autolytic activity.

A mutant of Staphylococcus aureus H (RUS3) uas isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. The rate of autolysis of whole cells and isolated cell walls of RUS3 was less than 10% of the parent strain. In addition, the ability of the crude soluble enzyme isolated from RUS3 to degrade cell walls was negligible compared with the parent strain. The cell wall composition and the generation time of RUS3 were comparable to the parent strain. Unlike S. aureus H, RUS3 grew in clumps and did not undergo cell wall turnover. Both strains exhibited identical kinetics of killing by penicillin G. This may indicate that autolytic enzymes play a role in cell wall turnover and cell separation, but in S. aureus most of the autolytic activity is unrelated to the lethal effect of cell wall antibiotics.

Amidohydrolases↗
PubMed1976

Chemical composition and turnover of peptidoglycan in Neisseria gonorrhoeae.

The peptidoglycan of all four colonial types of a number of strains of Neisseria gonorrhoeae constituted 1 to 2% of the dry weight of the cell. The chemical composition of cell types examined was similar with molar ratios of 1:1:2:1:1 for muramic acid, glucosamine, alanine, glutamic acid, and diaminopimelic acid, respectively. Ninety-six percent of the mass of the peptidoglycan was composed of these compounds. A lipoprotein analogous to that observed in Escherichia coli was not detected. The chain length of the glycan varied from 80 to 110 disaccharide units. The peptide contained equimolar amounts of D- and L-alanine. The rate of turnover of peptidoglycan in strain RD5 was 50% per generation. Turnover proceeded without a lag and followed first-order kinetics.

Alanine↗
PubMed1976

Mechanism of autolysis of Neisseria gonorrhoeae.

The major autolysin(s) of Neisseria gonorrhoeae was solubilized from envelopes by extraction with 2% Triton X-100 containing 0.5 M NaCl. Neither Triton X-100 nor NaCl alone could effectively release the autolysin(s). The major autolysin is N-acetylmuramyl-L-alanine amidase (EC 3.5.1.28). The pH optimum for this reaction was broad, ranging from 5.5 to 8.5. Optimal hydrolysis of peptidoglycan occurred in 2% Triton X-100 in 0.1 M KCl. Attempts to purify the autolysin were unsuccessful. A rapid assay for enzyme activity was developed using radioactive cell walls as a substrate ([3H]diaminopimelic acid).

Amidohydrolases↗
PubMed1975

Epidemiology of antibiotic and heavy metal resistance in bacteria: resistance patterns in staphylococci isolated from populations not known to be exposed to heavy metals.

Staphylococci were isolated from clinical specimens obtained from patients not known to be exposed to abnormal levels of heavy metals. The antibiotic and heavy metal resistance patterns of these strains were determined by using a disk diffusion test and computer sorting. Though not absolute, an association of resistance to mercury and tetracycline in coagulase-negative strains was found, in contrast to resistance to copper and penicillin in coagulase-producing strains. A high degree of correlation was observed between the resistance to phenyl mercury and inorganic mercury, but no correlation was obtained between resistance to methylmercury and other metals. In general, strains resistant to many agents were usually coagulase negative. A possible mechanism and implications of these associations are considered.

Anti-Bacterial Agents↗
PubMed1975

Epidemiology of antibiotic and heavy metal resistance in bacteria: resistance patterns in staphylococci isolated from populations in Iraq exposed and not exposed to heavy metals or antibiotics.

Staphylococci were isolated from rural and urban populations in Iraq, which were not known to be exposed to either heavy metals or antibiotics. The antibiotic and heavy metal resistance patterns of these strains were analyzed in both mannitol-fermenting and nonfermenting strains. Over 90% of the strains were resistant to at least one of the following antibiotics: penicillin, chloramphenicol, erythromycin, tetracycline, cephalothin, lincomycin, or methicillin. In general, mannitol-fermenting strains were resistant to penicillin and cupric ions. Mannitol-negative strains were more frequently associated with mercuric ion and tetracycline resistance. Although resistance to penicillin and tetracycline can coexist, the combination of penicillin resistance and tetracycline resistance usually occurred in mannitol-negative strains. The possibility of selection of heavy metal-resistant strains due to exposure to toxic levels of methylmercury was examined. No significant increase in mercuric ion-resistant strains of staphylococci or Escherichia coli were detected in exposed populations as compared to control groups. The possible reasons for this result are discussed.

Anti-Bacterial Agents↗
PubMed1975

Transformation and transfection in lysogenic strains of Bacillus subtilis: evidence for selective induction of prophage in competent cells.

Lysogenic strains of Bacillus subtilis 168 were reduced in their level of transformation as compared to non-lysogenic strains. The level of transformation decreased even further if the competent lysogenic cells were allowed to incubate in growth media prior to selection on minimal agar. This reduction in the frequency of transformation was attributable to the selective elimination of transformed lysogenic cells from the competent population. Concurrent with the decrease in the number of transformants from a lysogenic competent population was the release of bacteriophage by these cells. The lysogenic bacteria demonstrated this dramatic release of bacteriophage only if the cells were grown to competence. Both the selective elimination of transformed lysogens and the induction of prophage was prevented by the inhibition of protein synthesis. Additionally, competent lysogenic cells released significantly higher amounts of exogenous donor transforming deoxyribonucleic acid than did competent non-lysogenic cells or competent lysogenic cells incubated with erythromycin. These data establish that the induction of the prophage from the competent lysogenic cells was responsible for the selective elmination of the lysogenic transformants. A model is presented that accounts for the induction of the prophage from competent lysogenic bacteria via the induction of a repair system. It is postulated that a repair system is induced or derepressed by the accumulation of gaps in the chromosomes of competent bacteria. This hypothetical enzyme(s) is ultimately responsible for the induction of the prophage and the selective elimination of transformants.

Azo Compounds↗
PubMed1975

Effect of lysogeny on transfection and transfection enhancement in Bacillus subtilis.

Strains of Bacillus subtilis 168 lysogenic for bacteriophage phi105 transfer with deoxyribonucleic acid (DNA) isolated from bacteriophage SPO2 at a higher efficiency than non-lysogenic strains. This enhancement of transfection was not the result of recombination between bacteriophages SPO2 and phi105. Superinfection marker rescue increased transfection with DNA from bacteriophage phi105 occurred simultaneously with the addition of the transfecting DNA. Again, this enhancement of transfection was not the result of recombination but rather a protection of the transfecting DNA by the superinfecting bacteriophage. The ability of the superinfecting bacteriophage to protect the transfecting DNA from inactivation was maximal when the bacteria were just becoming competent. Bacteriophage phi1 cannot replicate after the transfection of competent bacteria lacking a functional DNA replication system, whereas bacteriophage phi1 was able to replicate after infection of competent bacteria grown under comparable conditions. These observations support the hypothesis that GAPase and an inducible repair system play an important role in the development of competence.

Azo Compounds↗
PubMed1975

Autolysis of Neisseria gonorrhoeae.

Physiological conditions that would provide maximal rates of autolysis of Neisseria gonorrhoeae were examined. Autolysis was found to occur over a broad pH range with the optimum at pH 9.0 IN 0.05 M tris(hydroxymethyl)amino-methane-maleate buffer. The temperature optimum was found to be 40 C. Potassium ions greatly stimulated autolysis at a concentration of 0.01 M. Exposure of growing N. gonorrhoeae cells to penicillin, vancomycin, or D-cycloserine influenced the susceptibility to the autolysis, whereas chloramphenicol afforded some protection against autolysis. The primary structure of the peptidoglycan is composed of muramic acid/glutamic acid/alanine/diaminopimelic acid/glucosamine in approximate molar ratios of 1:1:2:1:1, respectively. Exogenous radioactive diaminopimelic acid, D-glucosamine, and D-alanine were incorporated into peptidoglycan. During autolysis these radioactive fragments were released from cells.

Alanine↗
PubMed1975

Transformation of Bacillus subtilis: transforming ability of deoxyribonucleic acid in lysates of L-forms or protoplasts.

The transformation of Bacillus subtilis by homologous deoxyribonucleic acid (DNA) made available by gently lysing a stable L-form or protoplast suspension was 3 to 10-fold more efficient than DNA isolated by conventional procedures. This increased transformation was not influenced by digestion with pronase, trypsin, or ribonuclease. Preincubation of isolated DNA with L-form lysates did not increase the transformation efficiency above that achieved with untreated, isolated DNA. In addition to displaying a higher efficiency of transformation, the DNA found in these gently prepared lysates was also able to co-transform heretofore unlinked markers at frequencies in excess of those found by congression. Comparison of the frequency of multiple marker transformations to single marker events as a function of DNA dilution conclusively proves that these markers originated from the same continuous strand of DNA.

Bacillus subtilis↗
PubMed1975

Soluble macromolecular complexes involving bacterial teichoic acids.

Cell wall and membrane teichoic acids from several bacteria formed soluble complexes with polysaccharides and bovine plasma in alkyl alcohol solutions. Polysaccharides which contain different monomeric units and anomeric configurations complexed with the teichoic acids, suggesting that the interaction is relatively nonspecific. Teichoic acids complexed glycogen or bovine plasma albumin in 50 to 97% ethanol solutions. The macromolecular association between teichoic acids and polysaccharides or proteins was independent of teichoic acid size over a threefold molecular weight range. Glycerol phosphates or an acid hydrolysate of teichoic acid would not complex to either glycogen or bovine plasma albumin in ethanol. The optimal interaction between glycogen and the Bacillus subtilis lipoteichoic acid occurred between pH 4.5 and 8.2. The ability of teichoic acids to bind polysaccharides and proteins in moderate dielectric constant solvents suggests that these polymers may serve as complexing agents for hydrophilic molecules found in membranes.

Bacillus subtilis↗
PubMed1975

Stability of pathogenic colony types of Neisseria gonorrhoeae in liquid culture by using the parameters of colonial morphology and deoxyribonucleic acid transformation.

This investigation describes the surveillance of the colonial stability of the pathogenic type 1 from the gonococcal strain F62 to the nonvirulent types 3 and 4 in different liquid media. The maintenance of the colony types was monitored by the parameters of colonial morphology and deoxyribonucleic acid-mediated transformation. During growth in a complex medium, Mueller-Hinton broth, only 46.7% of the gonococcal population remained as type 1 after 12 h. The greatest change in the type 1 colony-forming units correlated with the decline in viable count. The conversion process could not be prevented by the continual maintenance of the gonococcus in logarithmic growth. The frequency of transformation from PRO(minus) (proline) to PRO(plus) was proportional to this decrease in type 1 colony-forming units. In contrast to Mueller-Hinton medium, the chemically defined minimal medium Gonococcal Genetic Medium (GGM) was capable of maintaining approximately 90% of the gonococcal population in the type 1 colonial form after 16 h of growth, despite a decrease in the viable count. Although the percentage of type 1 appeared to remain constant in GGM, the apparent transformation frequency increased approximately 24-fold from 0 to 12 h of growth. GGM appears to stimulate or maintain competence, as evidenced by an eightfold increase in transformation when cells are exposed to deoxyribonucleic acid in GGM as compared to Mueller-Hinton.

Culture Media↗
PubMedDate not supplied

Genetic determinants of microbial resistance to antibiotics.

Emergence of antibiotic resistance is related to the ease of mutation, to the extent of exchange of genetic information in bacteria by conjugation, transformation, and transduction, and to the large-scale use of antimicrobial agents in the biosphere. In addition to the development of resistance through chromosomal mutation and exchange of chromosomal genes among organisms, there is a more profound enlargement of the gene pool by the dissemination and amplification of plasmids. Two examples of the exchange of antibiotic resistance are analyzed: the transfer of plasmids from Bacteroides fragilis to Escherichia coli and the emergence of antibiotic-resistant strains of STreptococcus pneumoniae. Plasmids encoding antibiotic resistance in B. fragilis were transferred to E. coli by DNA-mediated transformation and conjugation. The beta-lactamase in the transformants and transconjugants displayed the same substrate specificity and electrophoretic mobility as the donor strain. The plasmid apparently was integrated rapidly into the chromosome of the recipient strain. Multiple antibiotic-resistant strains of S. pneumoniae were analyzed for plasmids, and none were detected. Furthermore, no evidence of linkage between the traits of multiple antibiotic resistance was observed. beta-Lactamase was not detected in the penicillin-resistant strains; therefore, it is likely that the resistance in these strains was chromosomal rather than plasmid-mediated. The range of genetic exchange and the use of Koch's postulates in determining the genetic mechanism of antibiotic resistance are illustrated and discussed.

Bacteria↗
PubMedDate not supplied

Auxotypes and antibiotic susceptibility patterns of Neisseria gonorrhoeae from disseminated and local infections.

The arginine-hypoxanthine-uracil auxotype has been linked with the propensity of gonococci to cause disseminated infections. Gonococci recovered from 25 patients with disseminated gonococcal infections were compared with gonococci recovered from matched controls, patients with uncomplicated gonorrhea selected during the same month. Minimal inhibitory concentrations of penicillin, tetracycline, erythromycin, and ampicillin, and the nutritional requirements (auxotypes) for proline alone, arginine alone, arginine, hypoxanthine and uracil together, serine alone and cysteine-cystine (wild type) were analyzed by discriminant analysis. Significant susceptibility to penicillin characterized strains causing disseminated infection, and a proline requirement was the most common auxotype (48%) among strains isolated in Atlanta. Together the minimal inhibitory concentration of penicillin and the proline auxotype best separated the strains causing gonorrhea. The arginine-hypoxanthine-uracil auxotype was was found in only 24% of strains causing disseminated infections. A trait other than auxotype must determine the capacity of the organisms to disseminate.

Adult↗